Hello and welcome to the Seven Forums!
Can you please confirm for me that you cannot boot into Windows? If you can, consult with me immediately, and don't continue with this fix.
Please try to boot into Safe Mode:
Safe Mode
If you can boot into Safe Mode, try to perform a System Restore from Safe Mode: See method one here:
System Restore
If you cannot boot into Safe Mode, find a Windows Vista/7 installation disk. Boot into it and select Repair your Computer. Perform a System Restore from your disk, using method two here:
Safe Mode
If you do not have an installation disk, or your one does not have the Repair your Computer option, create a disk using the download here (option two):
System Repair Disc - Create
If your computer does not have a CD drive, perform the download method here,
System Repair Disc - Create but burn the files to a USB memory stick instead of a CD, and then boot into the boot menu, and select the USB device. Then perform a System Restore, using method two here:
System Restore
If System Restore has not helped, we need to use a manual fix.
Boot into your disk, using the methods outlines about > Repair your Computer > Command Prompt. Run the following Commands:
takeown /f C:\Windows\winsxs\pending.xml
cacls C:\Windows\winsxs\pending.xml /G {COMPUTER NAME\Username}:F
For example,
cacls C:\Windows\winsxs\pending.xml /G ANNAI\SAI:F
del C:\windows\winsxs\pending.xml
Once your computer is running again, stick with us. Tell me what method you used. Do not try to update your computer again until I tell you to.
Good luck!
Richard